Our objectives for this year are to investigate the nature of the interaction between vascular smooth muscle of brain arteries and hemoglobin and other neurotransmitters, to study the nature of actin-myosin coupling in vascular smooth muscle, to study the effect of ischemia on excitation-contraction coupling, to determine the effect of hyperoxygenation of blood in the presence of ischemia in cerebral vasospasm, and to study the constituents of subarachnoid hemorrhage that might cause cerebral vasospasm.